Board sailing has developed rapidly over the past several years into an exceedingly popular sport in many countries of the world. While there have been many changes in the configuration of the board, the basic technique is to position the sail for navigation in much the same manner as in a small boat. However, sailboards are so light that positioning the sail to create lift on the sail permits greater speed. The primary lift-creating technique is to "close the gap", which means to pull the mast back to render more acute the angle between the board and the bottom of the sail, while maintaining the sail in the optimum plane for forward motion. Making use of both the lifting vector as well as the forward vector increases speed.
Another major reason for closing the gap is to minimize the flow of air under the sail. Wind should either propel the sail forward or lift it. Wind passing under the sail is "wasted." If there is no spilling of wind under the sail, there is maximum propulsion, called the "end plate effect."
The boardsailor closes the gap by raking back the mast, while maintaining it generally perpendicular to the water, so that the foot of the sail is at or near the top of the board. The forward hand, whether the sailor is on the right or left side of the board, is the one stressed mostly in closing the gap. The stress imposed on the hands and arms causes shoulder strain, epicondylitis, commonly called "tennis elbow", tendinitis in the wrist and hand, and wrist strains by reason of the unaccustomed forward hand position on the boom. That is, the boom is generally horizontal and parallel to the board. The sailor grips the boom with the forward hand either over the boom or under deviating the wrist toward the thumb or little finger side of the hand. Both positions are unnatural and will, in time, lead to the stress-caused problems.
There is a need for a means to naturally grip the boom of a sailboard for long periods of time to ease the stress on the arms of the sailor. The problem is no different from stress encountered in the industrial workplace. As stated in Meagher, "Human Factors Engineering: Primer for Surgeon's Participation in Industrial Injury Prevention" (Contemporary Orthopedics 8:73-80; March 1984), holding the arm horizontally for the performance of work tasks increases muscle fatigue and strain if the moment arm is increased. The forward hand of the sailboard is generally horizontal and at a great moment arm. To ease the fatigue and strain, the hand should meet the wrist in a horizontal plane in the same neutral position that exists when the hand and arm are in a passive, dependent position beside the trunk, with flexors and extensors in balance. Also, Meagher points out, industrial handles should fit the curve of the flexed proximal interphalangeal joints to permit even application of force. That is, gripping a curved handle is less stressful over a long period than gripping a straight handle.
The prior art in sailboards includes a chuck for tightening the sail, but this device is used solely for rigging the sail, and is not used in sailing.
Another previous device is a hook attached to a wrist strap on the wrist which permits the sailor to hook the boom and give his hand a rest. Such devices are actually counter-productive, at least as far as shoulder, elbow, forearm and wrist problems of concern here are involved, because the forces are transmitted directly from the boom to the wrist.
At the present time, there is in widespread use harnesses that the sailor wears and hooks to the boom by means of a harness line. The harness allows the sailor to use his body weight to sheet in the sail, thereby sparing his upper extremities. However, these harnesses are not helpful in resolving the problems addressed in this invention, such as elbow, wrist and hand problems.
The problem of strain on arms and shoulders is addressed in U.S. Pat. No. 4,505,216, which shows an elongated flexible element connected to the mast and adapted to receive the user's body so that the user can lean back on the element to apply weight to the boom without using his hands. However, such a device can only be used under steady state conditions, and any tack or change in conditions requires the user to again grasp the boom. There is a need for a device to permit gripping the boom under all conditions with a minimum of straining on upper extremities.